The present invention relates to a distributed processing system in which a plurality of processors having communication functions are connected to each other through a transmission line, and the processors respectively execute assigned processes by using memories while transmitting/receiving data to/from each other.
In a distributed processing system of this type, a plurality of processors respectively execute assigned processes by executing programs. In executing a program, each processor executes a process while accessing the assigned memory.
In general, in such a distributed processing system, each processor cannot access memories other than the assigned memory (first example). According to another system, as disclosed in, e.g., Japanese Patent Laid-Open No. 5-290001, a processor which is executing a program inquires of another processor about the used state of the memory assigned thereto. If the memory has an available area, the processor which has inquired uses the available area instead of its own memory (second example).
In the first example, when a memory shortage occurs in a processor which is executing a program, the processor cannot use a memory area of another processor even if it is available. For this reason, the memory capacity must be increased for each processor. An economical system cannot therefore be realized.
In the second example, each processor can use the memory of another processor. Even if, however, a memory area becomes available in a given processor while it is using the memory of another processor, the given processor must keep using the memory of another processor until the process under execution is completed. In this case, since this processor must access the memory of another processor through a transmission line, it takes time to access the memory. As a result, the execution of the process is delayed.